The human DR antigens, which are the analogues of the murine I region encoded molecules, have been under extensive investigation in our laboratory for approximately two years. During that time, we have developed not only a battery of cell lines but hybridoma antibodies that can be utilized to dissect this complex region of the human sixth chromosome in genetic and molecular terms. This proposal is a direct outgrowth of work previously done in the murine system and attempts to relate the human DR antigens to their murine counterparts. Primary structural analysis will be undertaken to compare products of different alleles and different loci. These studies are essential to a molecular understanding of the human immune response system and in order to provide information for DNA studies which are underway both in our own lab and elsewhere.